Motor vehicle air inlets serve for controlling the warm-up behaviour of the engine in that the air flow, for example, to the heat exchanger. Such air inlets are controlled via adjustable closing elements. By closing the fresh-air supply during warm-up or by controlling the amount of cooling air in accordance with the engine temperature, the optimum operating temperature is reached more quickly or is kept within a desired temperature range.
Such closing elements are mounted on the front side of a vehicle such that its engine compartment can be tightly closed, the drag coefficient is improved in the closed position of the closing elements and the engine reaches its operating temperature more quickly.
A closing element of this type is known from German Patent Publication No. DE 10 2008 049 010. Its centrally arranged actuator serves for the oppositely directed pivoting movement of groups of lamellae arranged above one another. In order to pivot in the same direction a plurality of lamellae arranged parallel to one another, each of them has, at a distance from its pivot axis, a driver journal which is connected to a common coupling element. The pivoting drive takes place here by the direct coupling of the rotary axle of one of the lamellae to the output shaft of a stepping motor.
An advantage of this construction lies in the space-saving, central arrangement of the actuator within the frame and in the consequently symmetrical distribution of the adjusting force of the actuator to closing elements which are relatively short and thus subjected to relatively high loading by bending and torsion forces. Such forces arise not only as a result of the ram pressure on the vehicle front end or as a result of the effect of impact forces by impacting foreign bodies, but also as a result of the adjusting force of the actuator if some lamellae are sluggish due to contamination or have to be broken loose after freezing up.
German Patent Publication No. DE 10 2012 214 474 A1 discloses a controllable air inlet for a motor vehicle, wherein at least one closing element which is pivotable about a longitudinal axis is mounted at each of its free ends in a bearing receptacle. The free ends of the closing element are formed substantially as cylindrical journals, with the result that the at least one pivotable closing element is displaceable in the axial direction, within the component tolerances. In the case of high speeds of the vehicle and correspondingly large wind forces, there occurs flapping, rattling or even lifting of the pivotable element, which leads to undesired noise generation.
It is also possible to produce the air inlet as a composite structure consisting of plastic and metal in order to reduce flapping, rattling or lifting, but this leads to an undesired weight increase of the air inlet.